Phosphate recovery in reverse flotation using a fluosilicate to deactivate the reagents



PHOSPHATE RECOVERY IN REVERSE FLOTATION USING A F LUOSILICATE TO DEACTIVATE THE REAGENTS William A. Hodges, Plant City, and Joseph E. Floyd,

Fort Meade, Fla., assignors to Swift & Company, Clucago,-lll., a corporation of Illinois No Drawing. Application January 24, 1955, Serial No. 483,828

15 Claims. (Cl. 209-166) The present application, which is a continuation-inpart of our earlier application, Serial No. 393,012, filed November 18, 1953, and now abandoned, relates in general to the concentration of phosphate-beating minerals from their ores, and more specifically to an improvement in the so-called reverse flotation method of phosphate recovery.

It has heretofore been proposed, and generally followed in the field of phosphate recovery, to subject the phosphate ore to a concentration step wherein the bulk of the phosphate values is floated in a rougher concentrate along with a minor proportion of silicious gangue, followed by a second concentration step wherein this rougher concentrate is repulped and the silicious gangue floated therefrom. In performing the first step in this process negative-ion reagents, such as the higher fatty acids, are used to selectively coat the phosphate particles, while in the second step positive-ion reagents, such as the higher aliphatic amines, are used to selectively coat the si'licious particles. A substantial improvement in the grade and recovery of the final concentrate results when the effect of the negative-ion reagents is removed prior to treatment of the rougher concentrate with the positive-ion reagents. This negative-ion reagent deadening step has heretofore been carried out only by the use of sulfuric acid treatment followed by a washing step, and it has been generally believed that the acid reaction is essential to the removal of the effect of the negative-ion reagents.

It has now been discovered that this is apparently not the case, and that a similar effect may be reproduced without the necessity of using sulfuric acid. The conventional use of sulfuric acid causes an increase in the amount of amine reagent required to float the silica due to the reaction between the amine and the residual acid carried over from the washing step to form an insoluble salt having practically no silica floating power.

It is therefore an object of the present invention to provide a method for deactivating negative-ion reagents in a reverse flotation process for the recovery of phosphatic values wherein sulfuric acid is not required.

It is a further object of the present invention to provide a method for deactivating negative-ion reagents in a reverse flotation process for the recovery of phosphatic values wherein a by-product, produced during the resultant treatment of the phosphatic material, is used.

Additional objects, if not specifically set forth herein, will be readily apparent to one skilled in the art from the following detailed description of the invention.

In accordance with the present invention fluosilicates,

such as the metal fluosilicates, including alkali metal and alkaline earth fluosilicates, may be used for deactivating the negative-ion reagents in a reverse flotation process. Obviously, since as stated above, the function of the fluosilicate is to deactivate the negative ion reagent, this fluosilicate must itself be ionizable in Water and hence watersoluble. By this term water-soluble it is meant that the solubility of the fluosilicate must be suflicient to deactivate the negative ion reagents. In the case of some of nited States Patent these fluosilicates, such as calcium and potassium, the solubility may be only a very small amount. It has been found, for example, that any of the various salts, calcium fluosilicate (CaSiFs), potassium fluosilicate (K2SiFe), ammonium fluosilicate ((NH4)2SiFs), magnesium fluosilicate (MgSiFs), or sodium fluosilicate (NazSiFs), any of which may be produced from the phosphoric acid made from the recovered phosphatic values, are very effective for use in the invention. These reagents, in quantities as small as one-third the amount by weight of sulphuric acid conventionally required, will produce a similar deactivating of the negative-ion reagents. In addition, the use of these salts does not cause an extensive depression in the pH of the rougher concentrate as does the use of the conventional sulfuric acid and, if carried over from the washings, they do not adversely affect the amine reagent as does the mineral acid. Accordingly, less amine reagent is required to satisfactorily treat a rougher concentrate which has been deactivated with one of these fluosilicates than is required when the deactivation is carried outwith sulfuric acid.

The amount of fluosilicate may vary considerably. A suflicient amount to counteract the negative ions will usually range between about 1 and 5 pounds per ton of finished concentrate. The preferred amount is about 2 to 3 pounds.

The deactivators of the present invention, as aforesaid, may be produced as by-products from phosphoric acid which is manufactured from the phosphatic values recovered in the floatation operation. For example, the recovery operation for sodium silico fluoride, which does not form a part of the present invention, comprises adding either sodium hydroxide or a sodium salt, e. g., NaCl or NazCOs, to the phosphoric acid and filtering, washing, and drying the resulting sodium silico fluoride precipitate. While the present invention contemplates primarily the use of fluosilicates obtained from this source and hereinafter referred to as by-product fluosilicates, it is also within the scope of the present invention to use C. P. fluosilicates and other preparations of such compounds regardless of the source thereof.

The following examples show the effectiveness of the present method under varying conditions as compared with the conventional method using sulfuric acid. These examples are furnished for the purpose of illustration only and are not to be construed as placing any limitation on the scope of the invention other than as appears in the appended claims.

Example I Silica floats were run on rougher concentrates following deactivation of the negative-ion reagents in such concentrates by the use of sodium silico fluoride in accordance with the present invention. Similar floats were run on rougher concentrates after using the conventional mineral acid deactivation treatment. in both instances the original feeds were approximately identical. The same amounts and types of negative-ion reagents were used in obtaining the rougher concentrates, and the same positive-ion reagent (amine) was used in obtaining the silica float. Under column (a) of the following table are grouped the test data obtained by conditioning a rougher concentrate containing negative-ion reagents at about 60-65 percent solids with 2 pounds NazSiFs/ton of conmmwmma7mmmm ouuuuarrita S1-l 1 8 sodium silico mmmwwoowwmm U 5 0 2 0 9 7 0 &L 0 %1072 The results were was conducted in the same manner as tests (0) of Examples I and II.

020309898 m2182oo945 concentrate as in test (a), and the silica floated as in the case of the preceding runs.

of concentrates, the deadened reagents washed from the Pounds NaOH/ton concentrates.". Pounds Amine/ton concentrates. r.

Example IV The foregoing tests reported in Examples I-III were made using by-produet sodium silico fluoride as the de activating agent for the negative-ion reagents. A further series of tests was conducted to illustrate the use of chemi- 5 cally pure sodium silico fluoride. Test (a) was conducted in the same manner as tests (a) of the previous examples, except that C. P. sodium silico fluoride was substituted for the by-product sodium silico fluoride used in such Test ([1) was run in an identical manner to that hat the amount of C. P. fluoride was increased from 2 to 3 pounds/ton concen- Test (0) was the conventional run using a mineral acid as the deactivating agent and was conducted in the manner of the conventional runs reported in the previous examples.

tests.

tratcs.

40 Percent solids in washing step...

The rougher concentrates Example V ashed free of deadened reagents by Test with th ine) Test (c) was Pounds Reagents/ton Cone:

ent (am Test (c) is the same as (a) Test ((1) is the comparative stained when the amount of 30 0f except Y mineral acid is cut down to give substantially the same pH in the Washing step as was obtained when sodium silico fluoride was used.

Example II Similar tests were run on rougher concentrates containing negative-ion reagents to show the effects of varying 20 the pH of the concentrates in the silica float step and also e washing step as that obtained when soride is used. Under column (a) is reample 1. Test (b) Was run exactly the same as test (a) except that caustic soda was added ceatrate during the sill run in the same manner as test (0) of Example I. Test ported the results of a test conducted exactly as th reported as (a) in EX of reducing the conventional amount of acid to give the same pH in th dium silico line to the con (d) shows the results 0 Percent solids in Washing step.

pH washing stop.....

Pounds reagents/ton concentrates:

recovered...

n n s n H S O m Mn N r HOS t nnmL in 9 a mnR n. mmm w. sm t m t am ream PiBBBfiP Test ([2) is the same as (a) Example III Similar tests were run on rougher concentrates containgative-ion reagents to show that good results can mount of anionic or positive-ion reagent is drastically reduced in the subsequent silica float. (a) was run in the same manner as the tests reported as (a) in Examples 1 and II.

was reduced by 50 percent. except that the amount of positive-ion reag was reduced by percent run using the conventional mineral acid deactivation and lag ne be obtained using the deactivator sodium silico even when the a except that the amount of positive-ion reagent (amine) J 0 5575 0 & MAUI. Sou-aroma. .r I distal & 00 317 4 0 g (1 6 t 2 734 045 F e o ml 79.0735 .1 Iain-a1 m. 8W7 49 U r 8 3" 45oomnow .1 12cm 7 M s 200 81.7 4W K 281400 N 818837 .1 7 emLrm s 200 9on7 A m 8 C 37494 1 mum 186317 RWLO L .20 W97 49 m s e t n n e c C t n m 1 e P These last-described tests indicate that, while all the fluosilicates are applicable, sodium fluosilicate produces slightly superior metallurgical results.

As can be seen from the foregoing examples, the method of the present invention not only provides a valuable use for a hitherto little-used by-product, but it also permits a reduction in the amount of expensive amine reagent required in the silica flotation step without a cor responding reduction in yield or quality of the recovered concentrate. Substantially smaller amounts of these reagents, the fluosilicates, may be used than are required when the conventional sulfuric acid is employed.

The type of flotation reagents, i. e., anionic or cationic, frothers, etc., used in either the initial phosphate float or the subsequent silica float does not form a part of the present invention and is not critical to its operability. Any of the conventional reagents heretofore known may be used in their customary and usual amounts with good success. In obtaining the rougher concentrates used in the above examples, the feeds were treated in the conventional manner with higher fatty acids, caustic soda, and fuel oil.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process for concentrating phosphate values from phosphate ore by a reverse flotation process wherein a negative-ion reagent is used to separate a rougher concentrate rich in phosphate and lean in silicious impurities, the negative-ion reagent deactivated and a positiveion reagent used to separate the silicious impurities from the phosphate, the improvement which comprises treating the rougher concentrate with a water-soluble fluosilicate to deactivate said negative-ion reagent prior to sepa rating the silicious impurities with the positive-ion reagents.

2. The process of claim 1 wherein the fluosilicate is an alkali metal silicate.

3. The process of claim 1 wherein the fluosilicate is an alkaline earth fluosilicate.

4. A process for the concentration of phosphate values from phosphate ore which comprises: subjecting the ore to a flotation operation with negative-ion reagents to float off a rougher concentrate rich in phosphate values and containing small amounts of entrained silicious impurities; conditioning said rougher concentrate with a small amount of a water-soluble metal fluosilicate to destroy the effect of said negative-ion reagents; and thereafter subjecting said rougher concentrate to a further flotation operation with positive-ion reagents whereby said silicious impurities are floated 0E and a concentrate rich in phosphate values is obtained.

5. A process for the concentration of phosphate values from phosphate ore which comprises: subjecting the ore to a flotation operation in the presence of a higher fatty acid, caustic soda and fuel oil to float off a rougher concentrate rich in phosphate values and containing small amounts of entrained silicious impurities; conditioning said rougher concentrate with a small amount of a watersoluble fluosilicate to destroy the effect of the agents used in its production; and thereafter subjecting said rougher concentrate to a further flotation operation with a positive-ion reagent whereby said silicious impurities are floated off and a concentrate rich in phosphate values is obtained.

6. A process for the concentration of phosphate values from phosphate ore which comprises: subjecting the ore to a flotation operation with a reagent to float off a rougher concentrate rich in phosphate values and containing small amounts of entrained silicious impurities; conditioning said rougher concentrate with a small amount of a water-soluble fluosilicate to destroy the effect of said reagent; washing the said concentrate to remove the reagent so conditioned; and thereafter subjecting said washed rougher concentrate to a further flotation operation with a reagent whereby said silicious impurities are floated ofl and a concentrate rich in phosphate values is obtained.

7. A process for the concentration of phosphate values from phosphate ore which comprises: subjecting the ore to a flotation operation with a negative-ion reagent to float off a rougher concentrate rich in phosphate values and containing small amounts of entrained silicious impurities; conditioning said rougher concentrate with a small amount of a water-soluble fluosilicate to destroy the eifect of said negative-ion reagent; washing the said concentrate to remove the negative-ion reagent so conditioned; and thereafter subjecting said washed rougher concentrate to a further flotation operation with a positive-ion reagent whereby said silicious impurities are floated off and a concentrate rich in phosphate values is obtained.

8. A process for the recovery of phosphate values from phosphate ore which comprises: subjecting the ore to a concentrating operation in the presence of negative-ion reagents whereby a rougher concentrate rich in phosphate values and containing said negative-ion reagents and a small amount of silicious impurities is formed; conditioning said rougher concentrate with a small amount of sodium silico fluoride to destroy the effect of said negative-ion reagents; and thereafter subjecting said rougher concentrate to a further concentrating operation in the presence of positive-ion reagents whereby said siliceous impurities are removed and a concentrate is obtained which is rich in phosphate values.

9. In a reverse flotation process for the recovery of phosphate values from phosphate ore wherein the ore is first subjected to a concentration operation in the presence of negative-ion reagents followed by a second concentration operation in the presence of positive-ion reagents, the improvement which comprises: contacting the ore from the first concentration operation with a small amount of sodium silico fluoride to destroy the effect of the negative-ion reagents prior to subjecting the ore to the second concentration operation.

10. A process for the concentration of phosphate values from phosphate ore which comprises: subjecting the ore to a flotation operation with a reagent to float off a rougher concentrate rich in phosphate values and containing small amounts of entrained silicious impurities; conditioning said rougher concentrate with a small amount of a Water-soluble fluosilicate to destroy the effect of said reagent; and thereafter subjecting said rougher concentrate to a further flotation operation with a reagent whereby said silicious impurities are floated OE and a rougher concentrate rich in phosphate values is obtained.

11. The process of claim 10 wherein the fluosilicate is sodium fluosilicate.

12. The process of claim 10 wherein the fluosilicate is calcium fluosilicate.

13. The process of claim 10 wherein the fluosilicate is potassium fluosilicate.

14. The process of claim 10 wherein the fluosilicate is ammonium fluosilicate.

15. The process of claim 10 wherein the fluosilicate is magnesium fluosilicate.

References Cited in the file of this patent UNITED STATES PATENTS 2,414,815 Kennedy et al. Jan. 28, 1947 2,469,422 Weinig May 10, 1949 

1. IN A PROCESS FOR CONCENTRATING PHOSPHATE VALUES FROM PHOSPHATE ORE BY A REVERSE FLOTATION PROCESS WHEREIN A NEGATIVE-ION REAGENT IS USED TO SEPARATE A ROUGHER CONCENTRATE RICH IN PHOSPHATE AND LEAN IN, SILICIOUS IMPURITIES, THE NEGATIVE-ION REAGENT DEACTIVATED AND A POSITIVEION REAGENT USED TO SEPARATE THE SILICIOUS IMPURITIES FROM THE PHOSPHATE, THE IMPROVEMENT WHICH COMPRISES TREATING THE ROUGHER CONCENTRATE WITH A WATER-SOLUBLE FLUOSILICATE OT DEACTIVATE SAID NEGATIVE-ION REAGENT PRIOR TO SEPARATING THE SILICIOUS IMPURITIES WITH THE POSITIVE-ION REAGENTS. 